A MOSFET (metal oxide semiconductor field effect transistor) having a super-junction structure is known in a semiconductor device with a medium breakdown voltage and a semiconductor device with a high breakdown voltage. In this super-junction structure, a vertical p-type semiconductor region is provided inside an n-type semiconductor region so as to form a depletion layer, which has uniform electric field intensity, at an interface between n-type and p-type semiconductor regions, thereby ensuring a breakdown voltage. A MOSFET with such a structure is characterized in that on-resistance is smaller than that of a MOSFET with a normal structure.
However, with recent improvements in performance of semiconductor devices, it has been required to control an impurity concentration of an n-type semiconductor region and that of a p-type semiconductor region with high accuracy, which causes a problem such as a high-cost manufacturing process. Therefore, in the manufacturing process, it has been desired to obtain a semiconductor device capable of achieving low resistance without controlling impurity concentrations of n-type and p-type semiconductor regions with high accuracy.